1. Field of the Invention
The invention concerns the encapsulation of integrated circuit chips, notably with a view to incorporating them in a portable support.
2. Description of the Prior Art
The following is the usual technique for encapsulating integrated circuits designed to be incorporated, for example, into a chip card:
the chip is transferred either to a grid of metallic conductors or to a grid-patterned epoxy glass type of dielectric support bearing photo-etched printed conductors. These conductors have, firstly, a contact zone to which the rear face of a chip is soldered and, secondly, contact zones to which wires, made of gold or aluminium for example, are soldered, these wires being also soldered to output contacts of the chip. These conductors moreover form external connection terminals of the integrated circuit after encapsulation. The contact zones may also be soldered directly to the chip (by the so-called TAB technique);
the chip and its wires are partially or totally covered with a protection against mechanical and chemical aggression; this protection may be provided by an epoxy resin or a silicone resin;
the strip carrying the chips protected by the resin is punched out into individual micromodules;
the micromodule is bonded in a surface cavity made in a portable support made of plastic material, in such a way that the connection conductors remain accessible at the surface.
The plastic support may be made by injection molding (the plastic material is then, for example, ABS resin). It may also be made by machining. It may be made by rolling pre-punched sheets of plastic material (the punched slots are used notably to make the cavity house of the micromodule); in this case, the plastic material may be polyvinyl chloride.
Several problems are encountered in these techniques for assembling the module in its insertion support. A first problem is the risk that the resin protecting the chip might flow between the conductors when it is deposited. The overflow hinders the operations for assembling the module on its support. A second problem, in the case of a card, is the obligation to assemble the micromodule by bonding. The reliability of this mode of transfer is not ideal in view of the difference between the materials forming the card and those forming the micromodule. A third problem is the indefinite reproduction of the external dimensions of the micromodule which has to fit into a cavity with given dimensions (preferably very shallow) of the chip card.
The invention is aimed at improving the reliability of assembly, achieving reproducibility of the dimensions of the micromodule and reducing its height while, at the same time, preserving a fabrication method that is easy to implement.